Consumer Electronics Servicing

1) Use Hand Tools;2) Perform Mensuration and Calculation;3) Prepare and Interpret Technical Drawings;4) Practice Occupational Safety and Health; and

5) Maintain Tools and Equipment

These five common competencies are covered separately in five Lessons. As shown below, each Lesson is directed to the attainment of one or three learning outcomes:

 

Lesson 1 – Use Hand ToolsLO1. Prepare hand toolsLO 2. Use appropriate hand tools and test equipment

 

Lesson 2 – Perform Mensuration and CalculationsLO 1. Select measuring instrumentsLO 2. Carry out measurements and calculationsLO 3. Maintain measuring instruments

 

Lesson 3 – Prepare and Interpret Technical Drawings LO1. Identify different kinds of technical drawings LO2. Interpret technical drawing

LO3. Prepare/Make changes in electrical/electronic schematics and diagrams

  Lesson 4 – Practice Occupational Health and Safety

LO 1. Identify health hazards and ccupational risksLO 2.Observe occupational and safety practices 

Lesson 5 – Maintain Tools and EquipmentLO 1. Maintain hand tools and equipmentLO 2 Perform basic preventive maintenance of electronic tools and equipment

LESSON 1Use Hand Tools

Definition of Terms

Accidental - occurring unexpectedly, unintentionally, or by chance.Alternating current - an electric current that is continually varying in value and reversing its direction of flow at regular intervalAnode - a positive electrode of semiconductor deviceCapacitance - a property that exists whenever two conductors are separated by insulating material, permitting the storage of electricityCapacitor - a component designed intentionally to have a definite amount of capacitanceCircuit - an arrangement of one or more complete paths of electron flow.

Conductor - a wire, cable, or other body or medium that is suitable for carrying electric currentCurrent - the rate of transfer of electricity from one point to anotherDesoldering - a process of unsoldering unwanted parts or components in the circuit with the support of soldering toolDielectric material - a material that serves as insulator because it has poor electric conductivityDirect current - an electric current that flows in one directionDiscrete components- separated or individual componentsElectronics - a branch of science and technology that deals with the controlled flow of electronsFlammable - tending to burn quicklyHazards - risks; dangersMalfunction - not in normal functionality

Ohmmeter - an instrument that measures the amount of resistance in certain component or circuitsResistance - the opposition that a component or material offers to the flow currentResistor – a component designed intentionally to have a definite amount of resistanceSoldering - a process of joining two metals caused by heatSoldering technique - a right process in which the solder (lead) is being applied in a connection or in the printed circuit boardSplicing – connecting two lengths of conductorTechnician - a person skilled in mechanical or industrial techniques or in a particular technical fieldTool kit - a small bag or box equipped with hand toolsTroubleshooting - identifying and repairing faults in equipment

Troubleshooting - identifying and repairing faults in equipmentVoltage - the electrical pressure that existed between two points and capable of producing a flow of current when a close circuit is connected between the points.Voltmeter - an instrument that measures the amount of electromotive force in a component or circuit.

Acronyms

PCB – Printed Circuit BoardPPE – Personal Protective EquipmentVOM – Volt-Ohm-Milliameter

Basic Hand ToolsDriving of Tools1. Screwdrivers are hand tools specifically designed to insert and tighten, or to loosen and remove screws. A screwdriver comprises a head or tip, which engages with a screw, a mechanism to apply force by rotating the tip, and some way to position and support the screwdriver, the tip of which is shaped in to fit a particular type of screw.

a. Slotted Screwdriver is used to drive or fasten negative slotted screws.

b. Phillips Screwdriver – used to drive or fasten positive slotted screws. It is a screwdriver that could take greater torque and could provide tighter fastenings.

c. Jeweler's Screwdriver Set – is a set of small screw drivers composed of slotted and Phillips screwdrivers.

Soldering Tools1. Soldering Iron – is a device for applying heat to melt solder in attaching two metal parts. A soldering iron is composed of a heated metal tip and an insulated handle. For electrical work, wires are usually soldered to printed circuit boards, other wires, or small terminals. A low-power iron (20-30 Watts) is suitable for this work.

2. Soldering Tool Stand – is a place where the soldering iron is placed during usage. This will keep the soldering iron away from flammable materials. The stand often comes with a sponge used in cleaning the tip of the soldering iron.

3. Desoldering tool is used in removing soldered wires and components on printed circuit boards for troubleshooting and repair purposes.

Splicing Tools1. Long Nose is used for holding, bending, and stretching the lead of electronic component or connecting wires.

2. Side Cutter is a wire-cutting pliers, though they are not used to grab or turn anything, but are used to cut wires.

3. Wire Stripper is a pair of opposing blades much like scissors or wire cutters. The addition of a center notch makes it easier to cut the insulation without cutting the wire.

Boring Tools1. 12V Mini-Drill – is used to bore or drill holes in the printed circuit board (PCB) with sizes from 1/32” – 1/16”.

2. Portable Electric Drill is used for boring hole(s) in plastic or metal chassis with the used of drill bits having sizes from 1/6” to approximately 1/4”.

3. Metal Files These are hand tools having a series of sharp, parallel ridges or teeth. Most files have a narrow, pointed tang at one end to which a handle can be fitted.

· Flat File is parallel in width and tapered in thickness; they are used for flat surfaces and edges.

 · Half Round File is tapered in width and thickness, coming

to a point, and is narrower than a standard half round and used for filing inside of rings.

  · Round File - is also called rat-tail file which is gradually tapered and used for many tasks that require a round tool, such as enlarging round holes or cutting a scalloped edge

triangular file

flat file

half-round file

round file

Cutting Tools1. Utility Knife is a common tool used in cutting various trades and crafts for a variety of purposes.

2. Hacksaw is used for cutting metals. Some have pistol gripswhich keep the hacksaw firm and easy to grip. The small hand-held hacksaws consist of a metal arch with a handle thatfits around a narrow, rigid blade.

handlebladepistol grip

Auxiliary Tools1. Magnifying Glass is a convex lens which is used to produce a magnified image of an object. The lens is usually mounted on a frame with a handle. Roger Bacon is the original inventor of the magnifying glass. A magnifying glass works by creating a magnified virtual image of an object behind the lens. Some magnifying glasses are foldable with built-in light.

2. Paint Brush – made of bristles set in handle, use for cleaning dirty parts of a circuit or an object.

Electronic equipment 

a. Volt-Ohm-Milliammeter. It is an equipment that combines three functions: as a voltmeter that measures both ac and dc voltages; an ohmmeter that measures resistance; and milliammeter that measures small amount of dc current. As safety precautions in the maintenance of this instrument, the following should be observed:

  · Always rest the function switch at 250V AC if an OFF position is not available in the instrument.

  · For current and voltage measurements, always set the function switch in the correct setting which is a little higher than the expected current or

voltage present in the circuit.

  · Place the instrument in a cool dry place, away from any magnetic devices, and free from vibrations. 

  

Oscilloscope

Volt-Ohm-MilliammeterSignal generator

b. Oscilloscope. An oscilloscope (commonly abbreviated CRO, for cathode-ray oscilloscope, or scope) is a piece of electronic test equipment that allows signal voltages to be viewed, usually as a two-dimensional graph of one or more electrical potential differences (vertical axis) plotted as a function of time or of some other voltage (horizontal axis).

 c. Signal generator. A signal generator is a device which produces simple wave form

s.   Such devices contain an electronic oscillator, a circuit that is capable of creating a

repetitive waveform. These are typically used in simple electronics repair and design where they are used to stimulate a circuit under test. 

Oscilloscope and signal generator should be given regular checkup for at least once a week by connecting them in the power line. This will help prevent their components from having moisture that might cause trouble in their circuits. 

In any activity involving skills, it is a standard procedure that you must always use the right tool or equipment properly that would fit in a particular task. In spite of this reminder or caution, some students abuse the use of tools and still practice the following common faults that must NOT be done.

Common Faults in Using Hand Tools Pliers:ØDo not increase the handle length of pliers to gain more leverage. Use a larger pair of pliers or bolt cutters if necessary.ØDo not substitute pliers for a wrench when turning bolts and nuts. Pliers cannot grip these items properly and might cause a slip and create an accident.ØNever use pliers as a hammer on the handle. Such abuse is likely to result in cracks or breaks.ØCut hardened wires only with pliers designed for that purpose.ØAlways cut the wires in right angle. Never rock from side to side or bend wire back and forth against the cutting edges. 

Screwdrivers: Never use screwdrivers as a pry bar, chisel, and punch stirrer or scraper. Never use screwdrivers with broken or worn-out handles. Screwdrivers of these kinds should have tags to indicate that it is defective. Never use pliers on a screwdriver for extra leverage. Only use wrench or screwdrivers specifically designed for purpose.

Utility Knives/ Blades: Do not use dull blades because they require more force, thus are more likely to slip. Replace the blade when it starts to “tear” instead of cut. Never leave a knife unattended with the blade exposed. Don’t bend or apply side loads to blades by using them to open cans or loosen tight cover of containers. Blades are brittle and can snap easily.

USING TOOLS BASED ON THEIR FUNCTIONS AND OPERATION Whenever you perform a task in the workshop you must use personal protective clothing and equipment (PPE) that are appropriate for the task and which conforms with your local safety regulations and policies. Your skill in using tools and equipment will make your work less difficult and ensure that tasks are performed properly and safely. Hand Tools o screwdrivers, needle-nose pliers

Diagnostic Tools o Analog or digital Volt-Ohm-Milliammeter, power supply

Safety check Do not use flammable cleaners or water on electrical equipment. Make sure designated walkways are kept clear of any obstructions. Always wear protective clothing and use the appropriate safety equipment. Make sure that you understand and observe all legislative and personal safety procedures when carrying out the following tasks.

Proper Use of Hand Tools Use the proper type and size of screwdriver by matching it to the screw. Phillips and Flat Head are the most common types. Do not over tighten screws because the threads may become stripped.

Procedure in using a soldering iron 1. Preparing the soldering irona. Place the soldering iron on the stand before plugging it. b. Wait a few minutes for the soldering iron to attain its operating temperature of about 4000C.c. Wipe the tip of the soldering iron on the wet damp sponged. Melt a little solder (soldering lead – 60/40) on the tip of the iron.e. Wipe again the tip of the soldering iron on the wet damp sponge.

2. Soldering techniquea. Hold the soldering iron like a pen, near the base of the handle. b. Touch the soldering iron onto the joint to be soldered. c. Apply a small amount of solder onto the joint. d. Remove the solder, then the soldering iron, while keeping the joint in still position. e. Inspect the joint closely. It should look shiny and with a volcano shape.

Mounting and soldering of components on PCB Procedure in mounting and soldering components on printed circuit board 1. Carefully check the ready-made PCB against the diagram and inspect for any microscopic shorts or open paths. Do the remedial steps, if necessary. 2. Insert the two 33K, ¼-watt resistors as indicated in the diagram.3. Insert the two electrolytic capacitors in the PCB as shown in the diagram. Take note their polarity orientation.4. Mount the two NPN transistors in the PCB taking into consideration the proper orientation of their electrodes (emitter, base, and collector).5. Mount the two jumbo LEDs (Light-Emitting-Diodes) to the place intended for in the PCB.6. Remove the insulation of a 4-inch #22 black stranded hook-up wire with at least 1/8 of an inch on both ends. Insert the uninsulated part at one end for the negative supply. 7. Do the same as in step no. 6 using red hook-up wire for the positive supply.8. Let your work be checked by your teacher before making any soldering job. a. Solder the connections of your work following the procedure of proper soldering technique. Diagram and components of the blinker

Diagram and components of the blinker

Blinker circuit. (a) Schematic diagram(b) Parts list(c) Components’ lay out (top view) (d)Foil pattern on PCB (bottom view)

Disassembly and assembly of the circuit Desoldering At some stage, you will probably need to desolder a joint to remove or reposition A wire or component. The easiest and most common way is the use of desoldering pump.Shown below is the proper way of removing electronic components from the circuit using a desoldering tool.

Removing components in PCB using a desoldering pump (solder sucker) 1. Set the pump by pushing the spring-loaded plunger down

until it locks. 2. Apply both the pump nozzle and the tip of your soldering iron

to the joint. 3. Wait a second or two for the solder to melt. 4. Then press the button on the pump to release the plunger and suck the molten solder into the tool. 5. Repeat if necessary to remove as much solder as possible. 6. The pump will need emptying occasionally by unscrewing the

nozzle.

Perform Mensuration and Calculations

Electronics is a branch of technology that deals with many applications. Audio electronics, video electronics, digital, medical up to weapons and banking are covered by the influence of electronics. There are quite a number of components used in the application of electronics. To name a few of these electronic components are resistors, capacitors, inductors and semi-conductors.

TYPES OF RESISTORS

Wire-wound

Film

Carbon-composition resistors

Resistors in band

Precision

Metal-film

Variable Resistor (Slide type)

Variable Resistor (Rotary type)

The most commonly used electronic components in the field are known as resistors. Resistor is a discrete component that offers opposition to the flow of current. Resistors have different types in accordance with the material used like carbon-composition and the wirewound resistor. According to construction, we have the fixed resistor and the variable resistor.

Resistors are very common and are the cheapest electronic components in the market for so many years. Their features are so interesting and are very colorful. That’s why resistors are very popular among students studying electronics. One distinct feature of this resistance - giving component is the way its value is determined. It uses a set of colors which follows a code for its assumed resistance expressed in OHMS.

Carry out Measurement and Calculation

PERFORMANCE STANDARDS Appropriate measuring instruments are selected

to achieve required outcome. Accurate measurements are obtained for job specifications. Calculations needed to complete work task are performed using four fundamental operations. Instruments are read to the limit accuracy of the

tool.

Resistor color coded value is not absolute. The real resistance of the resistor is sometimes lower or higher than its color coded value but not to exceed its tolerance level. Tolerance is the limit on how far the real value of the resistor can deviate from its color coded value. It can be more or less but subjected to a tolerable limit. In the color coding chart there is a column for tolerance. Color gold is + or – 5%, silver is + or – 10 %, and the no color means + or – 20%.

Procedure in interpreting the tolerance of resistor 1. Identify the tolerance color of the resistor being analyzed. Assuming the color is gold which has a value of + or – 5%. 2. Convert the percentage into its decimal equivalent. 5% is equivalent to .053. Compute for the percentage of the color coded value. Assuming that the color coded value is 100 ohms ± 5%. So 100 x .05 = 5 4. For the + side, add 5 to the color coded value of 100. 100 + 5= 105 ohms That is the maximum deviation for that resistor. Beyond that, the resistor will not be fitted for the circuit which requires such tolerance. 5. For the – side, deduct 5 from the color coded value of 100.100 – 5 = 95 ohms That will be the minimum deviation for that particular resistor. Far beyond that the resistor will be considered to be defective. 6. Finally the value of the resistor with colors brown- black- brown – gold is 100 ohms with a deviation of +5 or -5. (95 ohms -105 ohms)

Resistor color coding gives us the color coded value of a given resistor as well as the maximum and minimum value as dictated by the tolerance but the actual resistance is still unknown to us. The actual value of the resistor and the recorded data will confirm the status of the resistor whether good or defective.

OHMMETER Ohmmeter is a measuring instrument used to determine the resistance

of a component or equipment. This instrument is a great help in knowing the actual resistance of the resistors we use in the two operation sheets. The commonly used ohmmeter in electro-electrical laboratories now nowadays isembedded in a multi-function testing instrument called the (Volt-Ohm-Milliammeter ) VOM. For this discussion the VOM will be used but confined only to the ohmmeter section.

Parts of an Ohmmeter 1. Pointer. It is the most important part of the ohmmeter. It indicates the value ofelectrical quantity that has been measured.

2. Ohmmeter Scale- Nonlinear scale where reading of the resistance is based. It is usually found in the uppermost part of the VOM.

Range Multiplier- The portion of the ohmmeter where the actual reading is being multiplied.

Zero Ohm Adjustment – It is the portion of the ohmmeter where it is adjusted when the pointer of the ohmmeter fails to point to zero.

Test Probe- Serves as the input portion of the ohmmeter. Red test probe becomes positive in some instances, while the black one is negative.

PROCEDURE ON HOW TO INTERPRET RESISTANCE READING IN AN OHMMETER 1. Know the value of individual calibration in the ohmmeter scale. An ohmmeter scale is nonlinear which means the value of one line or calibration may not be true to other lines. It is therefore proper to assign values to every line for proper and accurate interpretation

As shown in the illustration, the scale can be divided into eight areas where individual treatment has to be made. Several mathematical computations will be involved to show the manner how values of individual lines are resolved.

The areas involved are 0- 2, 2-10, 10 -20, 20-50, 50 – 100, 100- 200, 200 – 300, 300 – 500. Value of 1calibration = line distance / total calibrations involved

For 0- 2: Line distance = 2 Total no. of cal = 10 Value of 1 line = 2/10 = 0.2 For 2-10: Line Distance = 8 Total no. of cal = 16 Value of 1line = 8/16 = 0.5 For 10-20: Line Distance = 10 Total no. of cal = 10 Value of 1line= 10 /10 = 1

For 20 -50: Line Distance = 30 Total no. of cal = 15 Value of 1 line = 30/15 = 2.0

For 50-100: Line Distance = 50 Total no. of cal = 10 Value of 1 line = 50/10 = 5.0For 100 – 200: Line Distance = 100 Total no. of cal = 5 Value of 1 line = 100/5 = 20For 200-300: Line Distance= 100 Total no. of lines = 2 Value of 1 line = 100/2 = 50

For 300–500: Line Distance = 200 Total no. of cal= 2 Value of 1 line = 200/2 = 100

2. Identify the appropriate range multiplier to be used Range multiplier is from R X 1, R X 10, R X 100, R X 1K, and R X 10K. 3. Connect the metallic part of the test probes and take note if the pointer points at zero. If not, adjust the zero ohm adjustment to zero. 4. Make the necessary resistance measurements.

Maintain measuring instruments

PERFORMANCE STANDARDS

Measuring instruments are not dropped to avoid damage. Measuring instruments are cleaned before and after using Proper storage of instruments is undertaken according to the manufacturer’s specifications and standard operating procedure.

Measuring instruments in electronics are confined only to analog testers and sometimes digital millimeter. Either way the maintenance of these instruments is a priority in all electronics laboratory rooms.

Electronic Measuring Instruments Aside from hand tools, measuring instruments are also needed for more accurate and quality output. In this connection, three of the most used instruments are presented here for you to be familiar with their uses and the proper way of maintaining them.

Volt-Ohm-Milliammeter. It is equipment that combines three functions: as a voltmeter that measures both ac and dc voltages; an ohmmeter that measures resistance; and milliammeter that measures small amount of dc current. As safety precautions in the maintenance of this instrument, the following should be observed:

VOLT – OHM - Millimeter Always rest the function switch at 250V AC, if an OFF position is not available in the instrument. For current and voltage measurements, always set the function switch in the correct setting which is a little higher than the expected current or voltage present in the circuit. Place the instrument in a cool dry place, away from any magnetic devices, and free from vibrations.

Oscilloscope. An oscilloscope (commonly abbreviated CRO, for cathode-ray oscilloscope, or scope) is a piece of electronic test equipment that allows signal voltages to be viewed, usually as a two-dimensional graph of one or more electrical potential differences (vertical axis) plotted as a function of time or of some other voltage (horizontal axis).

Signal generator. A signal generator is a device which produces simple waveforms.

Such devices contain an electronic oscillator, a circuit that is capable of creating a repetitive waveform. These are typically used in simple electronics repair and design; where they are used to stimulate a circuit under test. Oscilloscope and signal generator should be given regular checkup for at least once a week by connecting them to the power line. This will help prevent their components from having moisture that might cause trouble in their circuits. In any activity involving skills, it is a standard procedure that you must always use the right tool or equipment properly that would fit in a particular task. In spite of this reminderor caution, some students abuse the use of tools and still practice the following common faults that must NOT be done.

Prepare and Interpret Technical Drawings

LEARNING OUTCOMES: At the end of this Lesson, you are expected to do the following:

LO 1. identify different kinds of technical drawings;LO 2. interpret technical drawing; andLO 3. prepare/ make changes on electrical/ electronicschematics and diagrams.

Fig. 1-1a. Schematic diagram of the 1-watt stereo amplifier.

Fig. 1-1b. Pictorial diagram of the 1-watt stereo amplifier.

To produce a quality and marketable electronic diagram, you have to follow the Electronic Drafting Standards which is the process of illustrating various kinds of circuits and wiring systems. The most common graphical languages used in the illustration of components in circuits and wiring systems are block, schematic, wiring, and pictorial diagrams.

Most symbols that you will encounter in laying out electronic diagrams are accepted as standard, but in some cases some manufacturers modify symbols and practices to suit a particular industrial policy while others use their own symbols to represent unique or special component and devices.

Schematic Symbols of Electronic Components Some of the electronic symbols that were mentioned earlier are shown in Fig. 1-2. You can use several electronic templates shown in Fig. 1-3 to help you in drawing these symbols.

Fig. 1-2. Schematic Symbols of Electronic Components.

Fig. 1-3. Electronic templates

Drawing instruments and their uses Drawing instruments are used in preparing accurate drawings. Quality drawing instruments can produce accurate and good and presentable drawings. Below is a list of some of the most common used drawing instruments and materials in electronic drafting.

1. Drawing board. A smooth board usually rectangular in shape provided with perfectly straight edge which is used as working edge on which the Tsquare is moved while making drawings.

2. T-square. A T-square consists of two parts namely the stock and the blade joined together at right angles to each other by means of screws. The stock is made to slide along the working edge and the blade moves on the drawing board. The working edge of a T-square is used to draw parallel lines, vertical lines or inclined lines at 30 or 60 degrees.

3. Drafting machine or drafter. In a drafting machine, the uses andadvantages of T-squares, scales, set squares, and protractors arecombined. One end of the drafter is clamped at the left top end of thedrawing board by a screw provided in the drafter.

4. Set squares. Set squares are generally made from plastic material. Theyare triangular in shape with one corner, a triangle. A pair of set squares(30 o- 60o) and 45o. They are used to draw lines at 30o, 60o and 45 to the vertical or horizontal. o

5. Protractor. Protractors are used to mark or measure angles between 0and 180o. They are semicircular in shape and are made of plastic. Protractors with circular shape are capable of marking and measuring 0 to360 o are also available in the market.